Two general principles for the repression of the harm and seriousness of burning combustible materials include: (i) the lowering of the materials tendency to kindle by treatment with a suitable composition, e.g. impregnation with a flame retardant, and (ii) extinguishing of the fire with a suitable liquid, solid or gaseous composition. Examples of the composition according to (i) include compositions containing e.g. organic phosphorous containing compounds, and according to (ii), e.g. bicarbonate, halogenated hydrocarbon and carbon dioxide containing compositions.
For a generally applicable fire-extinguishing composition, it is desirable that the composition has additional fire retarding properties in accordance with the first (i) general principle above. The reason for this is to be found in the mechanisms by which a fire spreads and re-ignites. A fire spreads by ignition of the material adjacent to the burning material, either by direct contact with the flames or indirectly by the heat radiation. Re-ignition is often caused, as in the case of e.g. re-ignition of e.g. a liquid petroleum fuel or oil, by local heating above the flash point caused by heat radiation or direct contact with a hot object or material. Hence, if the materials tendency to kindle is lowered by the fire-extinguishing composition, the spreading of the fire is inhibited and the extinguishing of the same facilitated. Furthermore, when the flames have been put out, the chances of subsequent re-ignition are diminished in comparison to the case of employment of fire-extinguishing means which are lacking additional fire retarding properties.
Additional desirable properties of a generally applicable fire-extinguishing composition, beside its effectiveness as flame retardant and fire extinguisher, include low toxicity, low environmental impact, low cost of composing constituents, easy preparation and handling, e.g. by firefighters, high stability enabling long term storage without decomposition and/or physical changes, e.g. precipitation, of the composition, suitable physicochemical properties, e.g. viscosity, density, tixotropy and lipophilicity, to allow facile and controlled application by e.g. the spraying through nozzles and/or pumping through fire-hoses, suitable physicochemical properties to allow effective fire-extinguishing of burning liquid hydrocarbons.
An additional desirable property of a generally applicable fire-extinguishing composition is a suitable pseudoplasticity or thixotropy to maximize the adhesion of the composition to the material adjacent to the burning material.
The most well known and used fire-extinguishing composition, which fulfills many of the above mentioned desired properties, is common water. When used in fire-fighting, water contacts burning objects which results in sufficient cooling such that the burning objects fall below their combustion or ignition temperatures, and new ignition is precluded. In addition, when water contacts hot objects, the water vaporizes to produce steam, which expands and expels the air necessary for combustion.
However, when a fire is extinguished by spraying water on the fire, only a part of the sprayed water is effective because of water loss, such as by run-off or evaporation. In addition, water is not suitable for the fire-fighting of burning liquid hydrocarbons, e.g. gasoline, as the generated steam causes an explosion-like increase and spread of the flames.
In order to improve the properties of water in flame proofing and fire-fighting applications, additives such as fire retarding chemicals, which may retard combustion for at least brief periods even after the water has evaporated, as well as having a direct fire-extinguishing effect, are being developed and are presently in use. Additional additives include, for example, thickening agents and different foam forming agents. Various forms of organic and inorganic phosphorous containing compounds represent commonly used fire retarding chemicals.
WO2011016773 A1 describes a composition comprising an organic phosphorous containing compound, an oil and a detergent for use in fire control applications. The phosphorous containing compound is a compound in which phosphorous is covalently bonded to nitrogen in the form of an amidoalkylphosphonic acid. Furthermore, in specific embodiments the amidoalkylphosphonic acid is provided as an ammonium chloride complex, which is previously described in EP1065309 A1. Disadvantages of the amidoalkylphosphonic acids essential for the composition disclosed in WO2011016773 A1 include a relatively high cost of production in comparison to e.g. the other components of the composition. Furthermore, the presence of chloride in exemplified embodiments is undesired in respect of toxicological and environmental factors.
WO2012105903 A1 describes a composition comprising an organic phosphorous containing compound and a rheology modifier. The phosphorous containing compound is a compound in which phosphorous is covalently bonded to nitrogen in the form of an amidoalkylphosphonic acid. Furthermore, in specific embodiments the amidoalkylphosphonic acid is provided as an ammonium chloride complex, which is previously described in EP1065309 A1. Disadvantages of the amidoalkylphosphonic acids essential for the composition disclosed in WO2012105903 A1 include a relatively high cost of production in comparison to e.g. the other components of the composition. Furthermore, the presence of chloride in exemplified embodiments is undesired in respect of toxicological and environmental factors.
Hence, improved aqueous formulations useful for fire fighting, including fire extinguishing and fire proofing, is desirable.